I've seen no problems in my non legit version but think it's fair to buy the product when starting to capitalise on the use of it.
What I do NOT understand and cannot accept in any way is that the legit program do not accept idb from pirated version. That must also be very counterproductive for hexray since many will stay away from legit since they cannot redo the hundreds of hours they might have done with pirated copy.
Of course I have no problem that they make it difficult to open a legit idb on a pirated .exe which they probably also do.
Export the database to an idc using the pirate copy, then take your legit copy and import it. The way they prevent pirate versions from working with legit ones is that they keep updating the format. I've discussed the anti-piracy stuff with ilfak a lot over the years. I even asked if he would be willing to clear the pirate flag when a user goes "legit" but he wasn't keen on it. IDA Pro is a really good product and has absolutely no competition. It's his choice not to sell it to you.
I worked for law firms for many years and have seen businesses close because of pirates. What if someone gave away all the professional tunes ever developed. Why would anyone pay a professional to tune? In the IDA case I'm sure the only reason the tricore bugs got fixed is that paying users found them and asked. The owners of hex-rays are not millionaires either. It's just a couple of really smart guys in Belgium with families to feed.
As for hundreds of hours spent on your databases you have to be careful with a known pirate version because it might self-corrupt over time. A contractor turned in his work only as an IDC but when I compared the changes I found all sorts of stuff he didn't touch had been messed up. So I asked for his original idb. At that point I learned it was a pirated version. Hex-rays said something to the effect of guess guys who use pirated versions have a few surprises waiting.